There’s been a few posts around here regarding the M2 that discusses some of its differences with the Maslow. Here’s a link to some recent discussion, noting that I haven’t seen any real information from them on what I discuss there, so I’m definitely NOT saying there’s an issue with the M2.
With that said, I think the 40% speed increase is mostly attributable to a faster z-axis than the stock system and that’s been available for some time from many sources, its not new to the M2. What’s new is to M2 is the use of GRBL as the motor controller firmware and that does provide a speed increase, but not nearly as much as having a faster z-axis does.